This invention relates to ultraviolet curable coating compositions. More particularly, this invention relates to ultraviolet curable coating compositions which are internally self-pigmentable and need no external pigmentation in order to evidence a white appearance that hides the substrate on application to the desired substrate.
Ultraviolet curable coating compositions are well known in the art. Their use has increased dramatically in recent years due to coating industry concerns about reducing polluting effluents. Another major concern has been a reduction in the amount of energy required to ultimately cure the coating to the desired degree of crosslinking. In non-pigmented coatings (clears) cure response has not been a problem in most instances apparently because clear coatings allow substantial through-and-through penetration of the film by the ultraviolet light. However, with pigmented coatings a different problem has arisen, particularly with white, titanium dioxide-based coatings. In these instances, cure response properties have in many cases been so reduced that the coating did not cure below the surface leaving a non cured liquid sub-surface, or the coating remained soft and tacky.
Thus, it is an object of this invention to prepare coating compositions which are curable under minimal applications of ultraviolet energy.
It is another object of this invention to prepare coating compositions which, while pigmented, are still curable without the employment of excessive amounts of incident ultraviolet radiation.
These and other objectives are obtained by preparing the compositions of the instant invention.